Abstract
The asymmetric unit of the title 1:2 co-crystal, C14H10O4S2·2C7H6O2, comprises half a mol-ecule of di-thiodi-benzoic acid [systematic name: 2-[(2-carb-oxy-phen-yl)disulfan-yl]benzoic acid, DTBA], as the mol-ecule is located about a twofold axis of symmetry, and a mol-ecule of benzoic acid (BA). The DTBA mol-ecule is twisted about the di-sulfide bond [the C-S-S-C torsion angle is -83.19 (8)°] resulting in a near perpendicular relationship between the benzene rings [dihedral angle = 71.19 (4)°]. The carb-oxy-lic acid group is almost co-planar with the benzene ring to which it is bonded [dihedral angle = 4.82 (12)°]. A similar near co-planar relationship pertains for the BA mol-ecule [dihedral angle = 3.65 (15)°]. Three-mol-ecule aggregates are formed in the crystal whereby two BA mol-ecules are connected to a DTBA mol-ecule via hy-droxy-O-H⋯O(hydroxy) hydrogen bonds and eight-membered {⋯HOC=O}2 synthons. These are connected into a supra-molecular layer in the ab plane through C-H⋯O inter-actions. The inter-actions between layers to consolidate the three-dimensional architecture are π-π stacking inter-actions between DTBA and BA rings [inter-centroid separation = 3.8093 (10) Å] and parallel DTBA-hy-droxy-O⋯π(BA) contacts [O⋯ring centroid separation = 3.9049 (14) Å]. The importance of the specified inter-actions as well as other weaker contacts, e.g. π-π and C-H⋯S, are indicated in the analysis of the calculated Hirshfeld surface and inter-action energies.
Highlights
The asymmetric unit of the title 1:2 co-crystal, C14H10O4S2Á2C7H6O2, comprises half a molecule of dithiodibenzoic acid [systematic name: 2-[(2-carboxyphenyl)disulfanyl]benzoic acid, DTBA], as the molecule is located about a twofold axis of symmetry, and a molecule of benzoic acid (BA)
The DTBA molecule is twisted about the disulfide bond [the C—S—S—C torsion angle is À83.19 (8)] resulting in a near perpendicular relationship between the benzene rings [dihedral angle = 71.19 (4)]
In a recent study, the characterization of the 2:1 co-crystal between 2,20-dithiodibenzoic acid (DTBA) and 3-chlorobenzoic acid showed the formation of a homo-synthon between two DTBA molecules with each of the terminal carboxylic acid residues of the two-molecule aggregate engaged in non-symmetric homo-synthons with two 3-chlorobenzoic acid molecules, giving rise to a hydrogenbonded four-molecule aggregation pattern (Tan & Tiekink, 2019)
Summary
Molecular recognition represents an essential aspect in the crystal engineering of co-crystals as it dictates how supramolecular aggregates are formed, whether through shape, size or functional complementarity, to give a distinct connectivity and pattern (Meng et al, 2008). Different crystalline outcomes may be envisaged and in terms of co-crystals, cocrystals involving the same molecules associating via a symmetric carboxylic acid homosynthon might be isolated, or a co-crystal comprising different molecules, via a nonsymmetric homo-synthon might be formed In this context, in a recent study, the characterization of the 2:1 co-crystal between 2,20-dithiodibenzoic acid (DTBA) and 3-chlorobenzoic acid showed the formation of a homo-synthon between two DTBA molecules with each of the terminal carboxylic acid residues of the two-molecule aggregate engaged in non-symmetric homo-synthons with two 3-chlorobenzoic acid molecules, giving rise to a hydrogenbonded four-molecule aggregation pattern (Tan & Tiekink, 2019). In continuation of these studies, the crystal and molecular structures of the title 1:2 co-crystal of DTBA and benzoic acid (BA) are described as well as an analysis of the calculated Hirshfeld surface and the calculation of some specific interaction energies through a computational chemistry approach
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